Last fall I planted winter wheat and rye without any powered, mechanized equipment. This involved furrowing and seeding. Unfortunately, most studies of sewing density are for large fields worked by tractors. They also assume modern, dwarf wheat. Since I had none of these, I tried out various densities. I wrote it all up in a post last fall, which you can read here. This is a short post to update on the growth of these crops this spring.
I tried a variety of densities, ranging from 8.5 to 85 lb/ac, as shown in the below figure.
Now that the wheat is over a foot high this spring, I can already see a difference in the densities. The sparsely sewn 8.5 lb/ac is not covering the ground densely enough to compete with weeds. Also, due to spotty germination, the wheat crop is patchy. The next greatest density (43 lb/ac) is looking very strong. It has the most even growth and coverage. The rows are clear enough that I was able to walk between the 8-in spacing with the furrow and knock down incipient weeds. The densest stand of 85 lb/ac doesn’t seem to be growing any denser than the rows sewn half as thickly. All of these rows were at 8-in spacing, which seems to work much better than the 16-in spacing of the next test. The wheat here does not grow dense enough to crowd out the weeds. Note how the rows with 43 lb/ac grow laterally more than the 85 lb/ac rows, outcompeting weeds a little better. This is due to tillering, discussed below.
I looked at each density to compare the tillering rate. Tillering is when a single plant sends out multiple shoots that end up being individual stalks of wheat. Modern dwarf wheat has a low tillering rate, meaning each seed sends up a single shoot, for the most part. Heritage wheat, sewn at lower densities, is supposed to tiller prolifically. This is supposed to be better for weed suppression and yield, as less seed needs to be sewn. But too sparsely seeded fields allow weeds to out-compete the wheat.
My wheat appears to have an inverse relationship between row density and tillering. The wheat is in 8-in rows for the first three plots. The most sparsely planted rows (8.5 lb/ac) have the densest tillers. The most densely planted rows (85 lb/ac) have the least. The mid-range density (43 lb/ac) seems to look like it has the most growth. The second plot of 43 lb/ac was planted in 16-in rows and the same seeds/ft density as the 85 lb/ac plot — it also has poor tillering. In the dense rows, little tillering happens and the wheat is simply single stalks in rows. In the mid-range, the seedlings are tillering more and expand out to cover the space between the rows. We won’t know the true results until harvest.